Sylvanna Devlin

(I’m writing a whole section on this. But here is the start.)

The interesting aspect to all informative writing is “hasn’t anyone else written this?”

Other than textbooks I presume?

Yes.

And I am writing one too.

Sound is a bunch of pressure waves moving air or liquid by vibrating molecules in its path.

(Interesting tidbit, physics treats air as a liquid because airflow is similar)

Audiophiles like myself refer to all frequencies and decibels of such pressure waves as sound.

You don’t have to hear it as far as we’re concerned!

But most normal people don’t refer to it at all. Or give much thought to vibrating air!

But if you think of traveling in a vehicle that shakes as vibrating you know what that is.

What you may not notice is that rattling sensation is also rattling the air!.

Causing sound vibrations.

What are “frequencies and decibels?”

Frequency is how many vibrations per second are being transmitted. Either from the mouth or machinery some vibrations travel quickly and cause a “high” hum. Which is why we call it frequency.

While we tend to view frequency the way a radio chart would have it, with bas at the bottom. It’s more accurate to view it as overlapping cosine waves.

What’s that? Isn’t that a maths term?

Yes it is. They’re the graphs that undulate endlessly.

(Sine waves remain consistent, as that often gets confused – so mathematically we often have a useful start and finish)

Audio starts at the source and eventually peters out

It’s so long a cosine wave is how it’s referred to. Like ocean waves.

Some frequencies we can hear, some only our dogs or cats (or birds) do. They are all vibrating air whether it’s detected by an ear drum or not.

Think of the last time you tried yelling at someone with earplugs in. That sound was certainly real! (And you might have given them a headache)

Now. Frequency is how close together those waves are, how fast the air is moving.

But decibels!

That’s the up and down size of those waves. The height.

But that height changes our perception and how much can be transferred to us tends to eventually fade.

So if you want to be loud you need a lot of decibels to keep a higher frequency going because it’s the decibels that eventually cause the whole thing to become smaller and smaller.

That’s why higher frequency sounds have a shorter “lifespan”

So if they’re very loud to start with (high decibels) they are an entirely different frequency by the time they are heard distantly.

Because as those waves sink down the speed collapses too.

Think of a wave machine.

At the start those fast and furious waves are mathematically described and visualized as that up and down wave. Cosine 

But at the other end they’re slower and smaller.

Like that cosine has a ratio to keep!

What’s interesting is lower frequency sounds are omnidirectional and travel through solid objects.

So if you want to rattle the windows you can do so from your living room with just slightly loud decibels.

But if you want to do it from far away you have to start loud and fast!

So it still shakes the hinges by the time it gets there.